﻿namespace Ln.Fram.Core.Helper;

public class Compare<T, C> : IEqualityComparer<T>
{
	private Func<T, C> _getField;
	public Compare(Func<T, C> getfield)
	{
		_getField = getfield;
	}
	public bool Equals(T? x, T? y)
	{
		return EqualityComparer<C>.Default.Equals(_getField(x!), _getField(y!));
	}

	public int GetHashCode(T obj)
	{
		return EqualityComparer<C>.Default.GetHashCode(_getField(obj)!);
	}
}
public static class DistinctHelper
{
	/// <summary>
	/// 自定义Distinct扩展方法
	/// </summary>
	/// <typeparam name="T">要去重的对象类</typeparam>
	/// <typeparam name="C">自定义去重的字段类型</typeparam>
	/// <param name="source">要去重的对象</param>
	/// <param name="getfield">获取自定义去重字段的委托</param>
	/// <returns></returns>
	public static IEnumerable<T> DistinctNew<T, C>(this IEnumerable<T> source, Func<T, C> getfield)
	{
		return source.Distinct(new Compare<T, C>(getfield));
	}
}
